The heavy elements ( Z > 30 ) are created in neutron ( n ) -capture processes that are predicted to happen at vastly different nucleosynthetic sites .
To study these processes in an environment different from the Milky Way , we targeted the n -capture elements in red giant branch stars in the Sculptor dwarf spheroidal galaxy .
Using ESO VLT/FLAMES spectra , we measured the chemical abundances of Y , Ba , La , Nd , and Eu in 98 stars covering the metalliticy range -2.4 < \text { [ Fe / H ] } < -0.9 .
This is the first paper in a series about the n -capture elements in dwarf galaxies , and here we focus on the relative and absolute timescales of the slow ( s ) - and rapid ( r ) -processes in Sculptor .
From the abundances of the s -process element Ba and the r -process element Eu , it is clear that the r -process enrichment occurred throughout the entire chemical evolution history of Sculptor .
Furthermore , there is no evidence for the r -process to be significantly delayed in time relative to core-collapse supernovae .
Neutron star mergers are therefore unlikely the dominant ( or only ) nucleosynthetic site of the r -process .
However , the products of the s -process only become apparent at \text { [ Fe / H ] } \approx - 2 in Sculptor , and the s -process becomes the dominant source of Ba at \text { [ Fe / H ] } \gtrsim - 2 .
We tested the use of [ Y/Mg ] and [ Ba/Mg ] as chemical clocks in Sculptor .
Similarly to what is observed in the Milky Way , [ Y/Mg ] and [ Ba/Mg ] increase towards younger ages .
However , there is an offset in the trends , where the abundance ratios of [ Y/Mg ] in Sculptor are significantly lower than those of the Milky Way at any given age .
This is most likely caused by metallicity dependence of yields from the s -process , as well as by a different relative contribution of the s -process to core-collapse supernovae in these galaxies .
Comparisons of our results with data of the Milky Way and the Fornax dwarf spheroidal galaxy furthermore show that these chemical clocks depend on both metallicity and environment .